Draculin

At dusk, vampire bats emerge from their resting places in Mexico, Central and South America to feed on blood from cows, pigs, horses, and birds, and occasionally humans.http://oz.irtc.org/ftp/pub/stills/1998-04-30/sh_bats.jpg

Draculin is a glycoprotein found in the saliva of the vampire bat Desmodus rotundus. Draculin is composed of 411 amino acids with a molecular weight of ~88.5kDa. It functions as an anticoagulant, inhibiting coagulation factors IX (IXa) and X (Xa), thus preventing the blood of the bitten victim from clotting during the blood meal.

The vampire bat is found throughout the Central and South America from Mexico to the tip of Argentina. At night, the bats emerge from their roosts in hollow trees or caves. Using echolocation for orientation, they detect the presence of prey with heat sensors located in the face. The bats will usually land near their resting prey and then hop or crawl toward it. Once they have reached their prey, which can include sleeping humans, they make a tiny incision in the skin with their razor-sharp incisor teeth. The incision usually goes unnoticed by the resting animals, and the bats subsequently lick the blood flowing from the tiny wound. A very strong anticoagulant in the saliva of vampire bats keeps the blood from clotting. Although the wounds themselves are usually not serious, infection may result. Vampire bats are considered pests in much of their range, as they frequently transmit rabies to livestock. Humans can also be infected.

The saliva of the common vampire bat, Desmodus rotundus, contains a compound that might yield a new drug for dissolving blood clots in stroke victims.http://cdn.physorg.com/newman/gfx/news/hires/2012/2-thenightlife.jpg

The anticoagulant used by these bats has received attention from researchers studying the blood clotting process. As early as in 1932, the saliva of the vampire bat (Desmodus rotundus) was known to lead to interference with the hemostatic mechanism of the host animal (1). In 1991, the DNA coding of four plasminogen activators present in the saliva of the vampire bat was completed. Of the four, recombinant D. rotundus salivary plasminogen activator alpha 1 (DSPA, desmoteplase) was investigated further (2-4).

Draculin is currently being explored in medicine as a treatment for stroke. Ischemic strokes account for 87% of strokes each year in the United States, affecting patients by clogging blood vessels in the brain and cutting off vital blood and oxygen flow. The current treatment, called tissue plasminogen activator or tPA, can only be administered within the first three hours of a stroke. After that time, doctors believe the risk of additional brain damage from tPA far outweighs its benefit. Draculin may extend this window of treatment opportunity because it has a half-life of about four hours (5,6), whereas tPA has a terminal plasma half-life of about 5 minutes.

Draculin is safe and well tolerated by recipients - none of whom grew fangs or began sleeping in coffins http://commons.wikimedia.org/wiki/File:Bela_Lugosi_as_Dracula-2.jpg

Current clinical trials with human patients are testing the effectiveness of DSPA up to nine hours after stroke onset (7). Phase I clinical trials have determined that Draculin is safe and well tolerated by recipients - none of whom grew fangs or began sleeping in coffins! Phase III studies at now in progress to determine the efficacy of Draculin in the treatment of stroke.